Stocks have been negative all day, but the selling accelerated after a closely watched index measuring U.S. manufacturing was weaker for September. The Institute for Supply Management's survey came in at 56.6, below the 58.5 economists had been looking for.

Investors moved quickly into U.S. government bonds. The yield on the 10-year Treasury note dropped to 2.41 percent from 2.49 percent late Tuesday, a big move. Gold prices rose as well, up $3.90, or 0.3 percent, to $1,215.50 an ounce.

"A lot of people though this economic data was going to be robust, so when it was weak, everyone moved to reposition," said Tom di Galoma, head of rates and credit trading at ED&F Man Capital.

Utility stocks, which tend to be attractive to investors during times of volatility because of their higher-than-average dividends, were among the few stocks higher Wednesday. The Dow Jones utility index, a collection of 15 utility companies, was up 1 percent.

News that the first case of Ebola was diagnosed in the U.S. reverberated through several industries. Airlines were among the hardest hit as investors feared people would be discouraged from traveling. American Airlines fell $1.24, or 3.5 percent, to $34.24 and Delta fell $1.16, or 4.2 percent, to $34.99.

Drugmakers developing potential vaccines or treatments for Ebola rose. Tekmira Pharmaceuticals jumped $4.79, or 20 percent, to $28.53 after the company said it may start clinical trials for an Ebola drug this year. NewLink Genetics, another company looking into Ebola treatments, rose $2.14, or 10 percent, to $23.56.

A purchasing managers survey by Markit showed that German manufacturing unexpectedly contracted in September, the latest sign that Europe is being affected by the sanctions on Russia. It was the first time German manufacturing contracted in 15 months.

Traders are gearing up for Thursday's European Central Bank policy meeting in Naples, Italy. Though no change in policy is anticipated, there will be great interest in what ECB President Mario Draghi says about possible monetary stimulus from the central bank following further weak inflation data.

Tokyo's Nikkei 225 index shed 0.6 percent to 16,082.25 after a survey showed business conditions deteriorated. Stock exchanges in Shanghai and Hong Kong were closed for China's National Day holiday. Pro-democracy protests are swelling in Hong Kong. Streets in the business district have closed in the biggest threat to Beijing's authority since China took control of the former British colony in 1997.

The price of benchmark U.S. oil rose 37 cents to $91.53 a barrel in New York Wednesday. The price dropped $3.41 on Tuesday to $91.16, pushed down by plentiful supplies and a rise in the U.S. dollar against other currencies.